A Wrinkle in Time is the first book in a series written by Madeleine L'Engle. The books are written for children but have a timeless appeal because of their characters, their universal themes, and their science fiction elements.
Time is very important in many science fiction stories, as they are often set in a time other than the present; however, in A Wrinkle in Time (despite the reference in the title), the time period does not matter. What matters more is place in time, as the characters move back and forth in space more than time. The entire story explores the idea that “a straight line is not the shortest distance between two points.”
The best way to characterize the time period of this novel is to say it is set in the present. At the time it was written, the present was the early 1960s, and that seems consistent with the everyday lives of the Murray family (such as what they eat and drink and what they wear).